The present invention relates to a tint laying device for use in a picture reproducing machine such as a color scanner and a color facsimile.
When a color original picture is reproduced, for example, by printing, color separation densities of patterns of the original picture are determined by halftone dot area rates of printing plates.
For example, when an original picture 1 shown in FIG. 1, wherein a bill part 1a, a head part 1ba body part 1c, wing parts, a cap part 1d, and a tassel part 1e of the cap of the original picture 1 are composed of 90% of yellow and 20% of magenta components, 30% of yellow and 50% of cyan components, 30% of yellow and 50% of cyan components, 50% of cyan and 50% of magenta components, 50% of yellow and 50% of magenta components, and 30% of cyan component, respectively, is printed by using color separation printing plates for yellow, magenta, cyan and black, hereinafter referred to as Y plate, M plate, C plate and K plate, each part is printed by the Y plate, M plate and/or C plate having the halftone dot area rates corresponding to the percentages of the color components, i.e. the bill part 1a by the K and the M plates having 90% and 20% of halftone dot area rates, respectively.
Therefore, the Y plate is so prepared that the halftone dot area rates of the bill and the head, the body and the cap parts 1a, 1b, 1c and 1d may be 90%, 30%, 30% and 50%, respectively. Thus, in the conventional method, the tint laying halftone screens 2 having the halftone dot area rates of 90%, 30% and 50% are cut away in the shapes of the bill, the head, the body and the cap parts. Then, the halftone screens 2 cut away are disposed to a base sheet 3, as shown in FIG. 2a, and then are photographed to obtain the Y plate. The other plates, M plate, C plate and K plate, are obtained by arranging the tint laying halftone screens 2 cut away in the necessary forms on the base sheets, as shown in FIGS. 2b, 2c and 2d, and photographing them, in the same manner as described above.
However, such a tint laying operation is rather a troublesome operation which requires high skill and a lot of patience, and in this operation the costly halftone screens having different halftone dot area rates are consumed in great quantities.